Instantaneous Irreversible Reaction Research Articles

The asymptotic status of the Sherwood-Pigford model in the theory of absorption with chemical reaction

The Sherwood-Pigford model for absorption accompanied by instantaneous irreversible chemical reaction is an essentially discontinuous one, where a moving front across which concentration gradients suffer a discontinuity is assumed to exist. The case where the reaction is both instantaneous and irreversible is a doubly singular one. In this paper, a boundary-layer analysis is developed which shows that, for irreversible reactions, the Sherwood-Pigford model equations are approached asymptotically for arbitrary kinetics when an appropriate time scale of the reaction becomes sufficiently small. It is also shown that the same limit is approached for arbitrary stoichiometry in the case of instantaneous reactions when the ratio of the interface to the bulk concentration of volatile component becomes sufficiently large. Finally, a general estimate is obtained of the thickness of the reaction zone (which is assumed to be zero in the Sherwood-Pigford model) for the general case where the reaction is neither instantaneous nor irreversible.

Nonisothermal gas absorption with chemical reaction

AbstractThe temperature rise at a gas‐liquid interface due to heat evolution and the relevant enhancement factor for gas absorption rate are analyzed for absorption, with an instantaneous irreversible reaction and with a first‐order irreversible reaction allowing for the temperature dependence of the major physicochemical properties. The analysis reveals that, unlike isothermal absorption, the film theory solutions with the replacement of any system parameters do not give a reasonable approximation to the realistic penetration theory solution, except in the case of the physical absorption regime. However, the modified Danckwerts analysis, in which the physicochemical properties are evaluated at the time‐averaged interface temperature, is shown to be useful in obtaining the approximate penetration theory solutions with satisfactory accuracy.

Gas absorption accompanied by an instantaneous irreversible reaction in laminar falling films of pseudoplastic liquids

AbstractGas absorption accompanied by an instantaneous irreversible chemical reaction into laminar falling films of power‐law liquids was studied theoretically. The convective‐diffusion equations for a solute gas and a liquid‐phase reactant were solved numerically and the numerical solution for the reaction factor was obtained as a function of the Graetz number, the concentration ratio, the diffusivity ratio and the power‐law index of the liquid.

Penetration model of gas absorption into slurry accompanied by an instantaneous irreversible chemical reaction

AbstractRecently, the problem of absorption of gases into nonhomogeneous solvents has drawn more attention than ever as it found in various fields such as flue gas scrubbing, hydroprocessing, coal conversion and medicine. Since the first treatment of this problem by Ramachandran and Sharma(1), several models based on the film concept have been proposed(2‐7). There is, however, no penetration theory for the evaluation of the rate of the absorption of a gas into a slurry containing suspended solid particles. In this paper, a penetration model is presented for the absorption of gas A into a slurry containing solid B with an instantaneous irreversible chemical reaction.

Intraparticle mass tranfer in weak acid ion‐exchanger

AbstractResin phase mass transfer in a weak acid ion‐exchanger was analyzed based on a shrinking core model. It was assumed that H‐form core and metallic ion‐form shell appear in sorption of metallic ion, while metallic ion‐form core and H‐form shell appear in regeneration of metallic ion‐type resin. At the moving boundary, instantaneous irreversible reaction occurs, namely, neutralization reaction in the sorption and the protonation reaction in the regeneration. The Nernst‐Planck equation was applied to the fluxes of ions diffusing through the shell and the analytical solutions of sorption and regeneration rates were derived by assuming a pseudo‐steady state diffusion. Those solutions agreed fairly well with the experimental results in R‐H‐NaOH system (sorption) and in R‐Na‐HCl, R‐Cu‐HCl and R‐Cu‐H2SO4 systems (regeneration).

Liquid-solid mass transfer in gas-liquid cocurrent flows through beds of small packings.

Rates of mass transfer from liquid phase to small particles (average diameter, 0.46-1.3 mm) were measured by use of ion-exchange reaction followed by instantaneous irreversible reaction at 30°C. Nitrogen gas and dilute aqueous solution of sodium hydroxide were fed into a shallow bed packed with a strong cation exchange resin. Volumetric mass transfer coefficients for gasliquid cocurrent upflow and downflow were almost identical at the same gas and liquid flowrates but became somewhat greater than those in liquid-full single phase flow. A unified correlation could be derived by arranging experimental data for three arrangements: liquid-full single phase flow, gas-liquid cocurrent upflow and downflow (trickle-bed).

Mass transfer in turbulent flow accompanied by instantaneous irreversible chemical reaction. Experimental

Mass transfer in turbulent flow accompanied by instantaneous irreversible chemical reaction. Experimental

Mass transfer in turbulent fluids accompanied by an instantaneous irreversible chemical reaction. Theory

Mass transfer in turbulent fluids accompanied by an instantaneous irreversible chemical reaction. Theory

Solvent extraction of hydrochloric acid by long-chain alkylamine in a stirred transfer cell.

Authors indicated previously that the interfacial rate process was significant in low concentration range of long-chain alkylamine for the extraction of hydrochloric acid in a horizontal rectangular channel contactor. This paper is concerned with the effects of interfacial rate process for the same extraction system in a stirred transfer cell. It was found from the analysis of the initial rate of extraction that the interfacial rate process was significant in the range of concentration of long-chain alkylamine lower than 0.1mol/l, while in the range of concentration of the amine higher than 0.2mol/l the interfacial rate process was assumed to be an instantaneous irreversible reaction. These experimental results were interpreted by the diffusion model, taking account of the interfacial rate process expressed by (1, 2) order irreversible reaction with respect to the interfacial concentrations of hydrochloric acid and long-chain alkylamine.

Heat Evolution Zone of Gas Absorption Accompanied by Exothermic Instantaneous Irreversible Reaction

Heat Evolution Zone of Gas Absorption Accompanied by Exothermic Instantaneous Irreversible Reaction

Intraparticle ion exchange mass transfer accompanied by instantaneous irreversible reaction

A model is proposed for intraparticle mass transfer of ion exchange coupled with instantaneous irreversible reaction. The theoretical equations are der

Turbulent absorption with instantaneous irreversible chemical reaction

The model of damped turbulence near a gas-liquid interface has been employed in an analysis of mass transfer in absorption with an instantaneous chemical reaction in the liquid. It has also been established that simplified formulas can be substituted for the exact solution without any significant error as long as the reaction plane does not lie too close to the edge of the diffusional sublayer.

GAS ABSORPTION ACCOMPANIED BY AN INSTANTANEOUS IRREVERSIBLE CHEMICAL REACTION IN LIOUID OF A FINITE DEPTH

A problem of mass transfer with an instantaneous irreversible reaction was solved by introducing a concept of negative concentration and sometransformation variables to change the problem of a moving boundary to that of a nonlinear differential equation and using the finite difference method. The solution thus obtained is in good agreement with that of Sherwood and Pigford in an initial period. In the latter half period, however, the moving velocity of the reaction plane is accelerated and the results deviate from those of Sherwood and Pig ford. The reactant in liquid is exhausted within a finite time. The movement of the reaction plane is verified from experiments.